Solar mean magnetic field of the chromosphere

Abstract

The Solar Mean Magnetic Field (SMMF) is the mean value of the line-of-sight (LOS) component of the solar vector magnetic field averaged over the visible hemisphere of the Sun. So far, the studies on SMMF have mostly been confined to the magnetic field measurements at the photosphere. In this study, we calculate and analyse the SMMF using magnetic field measurements at the chromosphere, in conjunction with that of photospheric measurements. For this purpose, we have used full-disk LOS magnetograms derived from spectropolarimetric observations carried out in Fe I 6301.5 Å and Ca II 8542 Å by the Synoptic Optical Long-term Investigations of the Sun (SOLIS)/Vector Spectromagnetograph (VSM) instrument during 2010–2017. It is found from this study that the SMMF at the chromosphere is weaker by a factor of 0.60 compared to the SMMF at the upper-photosphere. The correlation analysis between them gives a Pearson correlation coefficient of 0.80. The similarity and reduced intensity of the chromospheric SMMF with respect to the photospheric SMMF corroborate the idea that it is the source of the Interplanetary Magnetic Field (IMF).